Method for fabricating a switch structure

Abstract

A switch structure having a base surface; a first high density interconnect (HDI) plastic interconnect layer overlying the base surface layer; a cavity within the HDI plastic interconnect layer; at least one patterned shape memory alloy (SMA) layer overlying the HDI plastic interconnect layer and the cavity, and at least one patterned conductive layer over the at least one patterned SMA layer; a fixed contact pad within the cavity and attached to the base surface and a movable contact pad attached to a portion of the first patterned SMA layer within the cavity such that when the first and second patterned SMA layers and the first and second patterned metallized layers are in a first stable position, the movable contact pad touches the fixed contact pad, thereby providing an electrical connection and forming a closed switch. The structure has a second stable position in which the SMA and metallized layers are flexed away from the cavity so that the contact pads are not in contact and form an open switch.

What is claimed is:  
     
       1. A method for fabricating a switch structure comprising: 
       applying a plastic interconnect layer overlying a base surface;  
       forming a cavity extending in the plastic interconnect layer to the base surface;  
       filling the cavity with a removable filler material;  
       applying and patterning a shape metal alloy (SMA) layer over the plastic interconnect layer and the filler material;  
       applying and patterning a conductive layer over at least a portion of the SMA layer, wherein applying and patterning the SMA layer and applying and patterning the conductive layer result in at least one portion of the filler material not being covered by either the SMA layer or the conductive layer;  
       removing at least some of the removable filler material from the cavity;  
       annealing the SMA layer;  
       shaping the SMA layer and the conductive layer,  
       wherein annealing and shaping causes the SMA layer to contract and move the conductive layer further away from the base surface when sufficient electricity is applied to the SMA layer.  
     
     
       2. The method of  claim 1  further comprising applying a fixed contact pad to the base surface within the cavity, and applying a movable contact pad on the SMA layer within the cavity, wherein 
       annealing is performed in a non-oxidizing atmosphere, and  
       shaping the SMA layer and the conductive layer further comprises shaping the SMA layer and the conductive layer to form a first stable position whereby the SMA layer and the conductive layer move towards the base surface and the movable contact pad touches the fixed contact pad to provide an electrical connection between the movable and fixed contact pads.  
     
     
       3. The method of  claim 2  wherein shaping the SMA layer and the conductive layer forms a second stable position whereby the SMA layer and the conductive layer flex away from the base surface and the movable contact pad does not touch the fixed contact pad, thereby providing an open electrical connection between the movable and fixed contact pads. 
     
     
       4. The method of  claim 1  wherein the conductive layer comprises a first conductive layer and the SMA layer comprises a first SMA layer and further including: 
       applying and patterning a second plastic interconnect layer overlying the first conductive layer and the first SMA layer;  
       applying and patterning a second shape memory alloy (SMA) layer overlying the second plastic interconnect layer;  
       applying and patterning a second conductive layer overlying the second SMA layer;  
       annealing the second SMA layer,  
       wherein shaping the first SMA layer and first conductive layer further comprises shaping the second SMA layer and the second conductive layer such that when electricity is applied to the second SMA layer, the second SMA layer contracts and moves the first conductive layer closer to the base surface.  
     
     
       5. The method of  claim 4  wherein annealing the first and second SMA layers and shaping the first and second SMA and conductive layers creates a first stable position whereby the first SMA layer, the first conductive layer, the second SMA layer, and the second conductive layer flex towards the base surface and the movable contact pad touches the fixed contact pad and a second stable position whereby the first SMA layer, the first conductive layer, the second SMA layer, and the second conductive layer flex away from the base surface.